In the near future it will be possible to build artificial bodies, and some decades after that it will become possible to gradually replace the biology of our brains with more durable and capable nanomachinery. A diverse industry of brain-computer interfaces and artificial intelligences will arise and come to maturity along the way. Will we in fact largely become a species of intelligent machines within the next few centuries? By this I mean designed machines, as opposed to the evolved machines we presently are: entities that are human, but very distant from our present forms, functions, and limitations. When you design the machinery, rather than just working with what you have been given, an enormous range of possibilities open up. For one thing, even very complex machines can be designed to be far more robust and easily maintained than our biology, allowing a person-turned-machine-intelligence the option of an extremely long life expectancy.
Will there be a population-scale rush away from biology towards the new and better options for bodies and brains as soon as they become a practical concern? Some people think so, and I believe it is an inevitable transition given the far greater capabilities that could be provided by being more than merely biological. Perhaps not a rush, but a transition over time, leaving behind a disparate collection of Amish-like groups and poor communities that coexist and trade with the transitioned human societies. On the large scale people follow incentives: they buy the new tools that improve life, boost economic output, and add new options at an affordable price. Those groups with the greatest economic output grow to become the cultural mainstream over time. There's no reason to think that any of this will change, no matter whether society is running on silicon or neurons. Here is an interesting thought, though:
I spoke with Aubrey briefly on the topic of the future of humanity, and the potential scenarios (often discussed in the world of transhumanism and futurism) that might involve moving our human conscious into other substrates, giving us long-lasting silicon bodies and potentially moving our minds into computers that are more durable and reliable that our current biological grey matter.
It is Aubrey's belief that the desire to leave our biological substrate will diminish as the "down-sides" of remaining purely biological go down. In other words, when we can more-or-less live forever in our present bodies, Aubrey believes that we will likely not wish to remove ourselves from them. The negative aspects of "being made of meat" - as he aptly put it - would be mitigated by an absence of disease and an absence of the recurring damage which is the origin of aging itself.
Another way of looking at the incentives of moving from biology to machinery is that it is not just a matter of chasing something better, but also a matter of leaving something undesirable. Discomfort is a great motivator, and evading the terrible suffering and death caused by aging is important to many of those who look with hope to a transhumanist future. Given an industry of rejuvenation medicine and complete control over aging, disease, and pain, however, being a standard issue biological human begins to look like an indefinitely comfortable existence - barring rare fatal accidents, of course, but who goes through life thinking that will happen to them?
So the argument here is that medicine, and specifically the defeat of degenerative aging, will alter the incentive landscape in a way that leads more people to choose to remain biological, even when it is possible to become a machine intelligence with greater capabilities and durability. My estimate of the timelines is that rejuvenation will be a going concern a long way prior to the point at which slow, safe replacement of the brain's neurons with nanomachinery is possible. It's possible that the increased comfort provided by the removal of age-related suffering and death will slow down progress towards ways to move biology to machinery.
But we shall see. It is interesting to think about these things, but important not to lose sight of the fact that researchers still need to build the means to reverse degenerative aging. There are detailed plans to show what needs to be done in order to rejuvenate the old, there are plenty of researchers ready to jump in and perform the work if given funding, but resources and public interest are - as ever - lacking. The future only stays fascinating if you remain alive to see it, so consider helping to speed progress towards the means of human life extension.